/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_biquad_cascade_df1_q15.c
*
* Description:	Processing function for the
*				Q15 Biquad cascade DirectFormI(DF1) filter.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
*
* Version 0.0.5  2010/04/26
* 	 incorporated review comments and updated with latest CMSIS layer
*
* Version 0.0.3  2010/03/10
*    Initial version
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup BiquadCascadeDF1
 * @{
 */

/**
 * @brief Processing function for the Q15 Biquad cascade filter.
 * @param[in]  *S points to an instance of the Q15 Biquad cascade structure.
 * @param[in]  *pSrc points to the block of input data.
 * @param[out] *pDst points to the location where the output result is written.
 * @param[in]  blockSize number of samples to process per call.
 * @return none.
 *
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using a 64-bit internal accumulator.
 * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
 * The accumulator is then shifted by <code>postShift</code> bits to truncate the result to 1.15 format by discarding the low 16 bits.
 * Finally, the result is saturated to 1.15 format.
 *
 * \par
 * Refer to the function <code>arm_biquad_cascade_df1_fast_q15()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.
 */

void arm_biquad_cascade_df1_q15(
    const arm_biquad_casd_df1_inst_q15* S,
    q15_t* pSrc,
    q15_t* pDst,
    uint32_t blockSize)
{


#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	q15_t* pIn = pSrc;                             /*  Source pointer                               */
	q15_t* pOut = pDst;                            /*  Destination pointer                          */
	q31_t in;                                      /*  Temporary variable to hold input value       */
	q31_t out;                                     /*  Temporary variable to hold output value      */
	q31_t b0;                                      /*  Temporary variable to hold bo value          */
	q31_t b1, a1;                                  /*  Filter coefficients                          */
	q31_t state_in, state_out;                     /*  Filter state variables                       */
	q31_t acc_l, acc_h;
	q63_t acc;                                     /*  Accumulator                                  */
	int32_t lShift = (15 - (int32_t) S->postShift);       /*  Post shift                                   */
	q15_t* pState = S->pState;                     /*  State pointer                                */
	q15_t* pCoeffs = S->pCoeffs;                   /*  Coefficient pointer                          */
	uint32_t sample, stage = (uint32_t) S->numStages;     /*  Stage loop counter                           */
	int32_t uShift = (32 - lShift);

	do {
		/* Read the b0 and 0 coefficients using SIMD  */
		b0 = *__SIMD32(pCoeffs)++;

		/* Read the b1 and b2 coefficients using SIMD */
		b1 = *__SIMD32(pCoeffs)++;

		/* Read the a1 and a2 coefficients using SIMD */
		a1 = *__SIMD32(pCoeffs)++;

		/* Read the input state values from the state buffer:  x[n-1], x[n-2] */
		state_in = *__SIMD32(pState)++;

		/* Read the output state values from the state buffer:  y[n-1], y[n-2] */
		state_out = *__SIMD32(pState)--;

		/* Apply loop unrolling and compute 2 output values simultaneously. */
		/*      The variable acc hold output values that are being computed:
		 *
		 *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
		 *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
		 */
		sample = blockSize >> 1u;

		/* First part of the processing with loop unrolling.  Compute 2 outputs at a time.
		 ** a second loop below computes the remaining 1 sample. */
		while(sample > 0u) {

			/* Read the input */
			in = *__SIMD32(pIn)++;

			/* out =  b0 * x[n] + 0 * 0 */
			out = __SMUAD(b0, in);

			/* acc +=  b1 * x[n-1] +  b2 * x[n-2] + out */
			acc = __SMLALD(b1, state_in, out);
			/* acc +=  a1 * y[n-1] +  a2 * y[n-2] */
			acc = __SMLALD(a1, state_out, acc);

			/* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
			/* Calc lower part of acc */
			acc_l = acc & 0xffffffff;

			/* Calc upper part of acc */
			acc_h = (acc >> 32) & 0xffffffff;

			/* Apply shift for lower part of acc and upper part of acc */
			out = (uint32_t) acc_l >> lShift | acc_h << uShift;

			out = __SSAT(out, 16);

			/* Every time after the output is computed state should be updated. */
			/* The states should be updated as:  */
			/* Xn2 = Xn1    */
			/* Xn1 = Xn     */
			/* Yn2 = Yn1    */
			/* Yn1 = acc   */
			/* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
			/* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */

#ifndef  ARM_MATH_BIG_ENDIAN

			state_in = __PKHBT(in, state_in, 16);
			state_out = __PKHBT(out, state_out, 16);

#else

			state_in = __PKHBT(state_in >> 16, (in >> 16), 16);
			state_out = __PKHBT(state_out >> 16, (out), 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

			/* out =  b0 * x[n] + 0 * 0 */
			out = __SMUADX(b0, in);
			/* acc +=  b1 * x[n-1] +  b2 * x[n-2] + out */
			acc = __SMLALD(b1, state_in, out);
			/* acc +=  a1 * y[n-1] + a2 * y[n-2] */
			acc = __SMLALD(a1, state_out, acc);

			/* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
			/* Calc lower part of acc */
			acc_l = acc & 0xffffffff;

			/* Calc upper part of acc */
			acc_h = (acc >> 32) & 0xffffffff;

			/* Apply shift for lower part of acc and upper part of acc */
			out = (uint32_t) acc_l >> lShift | acc_h << uShift;

			out = __SSAT(out, 16);

			/* Store the output in the destination buffer. */

#ifndef  ARM_MATH_BIG_ENDIAN

			*__SIMD32(pOut)++ = __PKHBT(state_out, out, 16);

#else

			*__SIMD32(pOut)++ = __PKHBT(out, state_out >> 16, 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

			/* Every time after the output is computed state should be updated. */
			/* The states should be updated as:  */
			/* Xn2 = Xn1    */
			/* Xn1 = Xn     */
			/* Yn2 = Yn1    */
			/* Yn1 = acc   */
			/* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
			/* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */
#ifndef  ARM_MATH_BIG_ENDIAN

			state_in = __PKHBT(in >> 16, state_in, 16);
			state_out = __PKHBT(out, state_out, 16);

#else

			state_in = __PKHBT(state_in >> 16, in, 16);
			state_out = __PKHBT(state_out >> 16, out, 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */


			/* Decrement the loop counter */
			sample--;

		}

		/* If the blockSize is not a multiple of 2, compute any remaining output samples here.
		 ** No loop unrolling is used. */

		if((blockSize & 0x1u) != 0u) {
			/* Read the input */
			in = *pIn++;

			/* out =  b0 * x[n] + 0 * 0 */

#ifndef  ARM_MATH_BIG_ENDIAN

			out = __SMUAD(b0, in);

#else

			out = __SMUADX(b0, in);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

			/* acc =  b1 * x[n-1] + b2 * x[n-2] + out */
			acc = __SMLALD(b1, state_in, out);
			/* acc +=  a1 * y[n-1] + a2 * y[n-2] */
			acc = __SMLALD(a1, state_out, acc);

			/* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
			/* Calc lower part of acc */
			acc_l = acc & 0xffffffff;

			/* Calc upper part of acc */
			acc_h = (acc >> 32) & 0xffffffff;

			/* Apply shift for lower part of acc and upper part of acc */
			out = (uint32_t) acc_l >> lShift | acc_h << uShift;

			out = __SSAT(out, 16);

			/* Store the output in the destination buffer. */
			*pOut++ = (q15_t) out;

			/* Every time after the output is computed state should be updated. */
			/* The states should be updated as:  */
			/* Xn2 = Xn1    */
			/* Xn1 = Xn     */
			/* Yn2 = Yn1    */
			/* Yn1 = acc   */
			/* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
			/* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */

#ifndef  ARM_MATH_BIG_ENDIAN

			state_in = __PKHBT(in, state_in, 16);
			state_out = __PKHBT(out, state_out, 16);

#else

			state_in = __PKHBT(state_in >> 16, in, 16);
			state_out = __PKHBT(state_out >> 16, out, 16);

#endif /*   #ifndef  ARM_MATH_BIG_ENDIAN    */

		}

		/*  The first stage goes from the input wire to the output wire.  */
		/*  Subsequent numStages occur in-place in the output wire  */
		pIn = pDst;

		/* Reset the output pointer */
		pOut = pDst;

		/*  Store the updated state variables back into the state array */
		*__SIMD32(pState)++ = state_in;
		*__SIMD32(pState)++ = state_out;


		/* Decrement the loop counter */
		stage--;

	} while(stage > 0u);

#else

	/* Run the below code for Cortex-M0 */

	q15_t* pIn = pSrc;                             /*  Source pointer                               */
	q15_t* pOut = pDst;                            /*  Destination pointer                          */
	q15_t b0, b1, b2, a1, a2;                      /*  Filter coefficients           */
	q15_t Xn1, Xn2, Yn1, Yn2;                      /*  Filter state variables        */
	q15_t Xn;                                      /*  temporary input               */
	q63_t acc;                                     /*  Accumulator                                  */
	int32_t shift = (15 - (int32_t) S->postShift); /*  Post shift                                   */
	q15_t* pState = S->pState;                     /*  State pointer                                */
	q15_t* pCoeffs = S->pCoeffs;                   /*  Coefficient pointer                          */
	uint32_t sample, stage = (uint32_t) S->numStages;     /*  Stage loop counter                           */

	do {
		/* Reading the coefficients */
		b0 = *pCoeffs++;
		b1 = *pCoeffs++;
		b2 = *pCoeffs++;
		a1 = *pCoeffs++;
		a2 = *pCoeffs++;

		/* Reading the state values */
		Xn1 = pState[0];
		Xn2 = pState[1];
		Yn1 = pState[2];
		Yn2 = pState[3];

		/*      The variables acc holds the output value that is computed:
		 *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
		 */

		sample = blockSize;

		while(sample > 0u) {
			/* Read the input */
			Xn = *pIn++;

			/* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
			/* acc =  b0 * x[n] */
			acc = (q31_t) b0 * Xn;

			/* acc +=  b1 * x[n-1] */
			acc += (q31_t) b1 * Xn1;
			/* acc +=  b[2] * x[n-2] */
			acc += (q31_t) b2 * Xn2;
			/* acc +=  a1 * y[n-1] */
			acc += (q31_t) a1 * Yn1;
			/* acc +=  a2 * y[n-2] */
			acc += (q31_t) a2 * Yn2;

			/* The result is converted to 1.31  */
			acc = __SSAT((acc >> shift), 16);

			/* Every time after the output is computed state should be updated. */
			/* The states should be updated as:  */
			/* Xn2 = Xn1    */
			/* Xn1 = Xn     */
			/* Yn2 = Yn1    */
			/* Yn1 = acc    */
			Xn2 = Xn1;
			Xn1 = Xn;
			Yn2 = Yn1;
			Yn1 = (q15_t) acc;

			/* Store the output in the destination buffer. */
			*pOut++ = (q15_t) acc;

			/* decrement the loop counter */
			sample--;
		}

		/*  The first stage goes from the input buffer to the output buffer. */
		/*  Subsequent stages occur in-place in the output buffer */
		pIn = pDst;

		/* Reset to destination pointer */
		pOut = pDst;

		/*  Store the updated state variables back into the pState array */
		*pState++ = Xn1;
		*pState++ = Xn2;
		*pState++ = Yn1;
		*pState++ = Yn2;

	} while(--stage);

#endif /*     #ifndef ARM_MATH_CM0 */

}


/**
 * @} end of BiquadCascadeDF1 group
 */
